"You miss a big guy like him, you have to really get together and play as a unit out there," Rask said. "Missing (Chara) we have to play as a unit, and we did that today and it paid off big time."
After a moving pregame ceremony to honor two fallen soldiers, Toronto quickly fell flat and drew boos from the crowd after the Bruins went ahead 4-0 early in the third period.
"It's the rink that I grew up watching games in and dreaming of being in the NHL, so it was an awesome feeling," said Hamilton, a Toronto native.
Richard Panik beat Rask with 5:33 remaining, on a delayed power play, slapping in a rebound from in close for his first with the Maple Leafs.
Toronto showed some spark after that but it was too late. Eight games into the season, the Maple Leafs are leaking goals at home and searching for answers.
The door to the dressing room was closed longer than usual after the latest Toronto loss.
"Frustration, anger. Those are two things front and center that were probably from the coaching staff's perspective," coach Randy Carlyle said when asked for his emotions. "We didn't win too many battles early in the hockey game."
Toronto is 2-0-1 on the road but only 1-4 at home where the Maple Leafs have been outscored 19-10 and have allowed at least four goals four times.
"No explanation. I think we're two different teams on the road and home for some reason," center Nazem Kadri said.
"We've got to find a way to become a lot more consistent because one good game, one bad game, one OK game here, one OK game there is just not good enough in this league," captain Dion Phaneuf said. "We are finding that out right now."
Rask, the reigning Vezina Trophy winner, is 10-2 in 14 outings against Toronto. He came into the game with a .943 save percentage and 1.64 goals-against average against the Leafs.
Toronto goalie Jonathan Bernier left early in the third period after giving up four goals on 25 shots.
Both teams finished with 33 shots.
Boston has won 12 of the past 16 regular-season games (12-2-2) against the Leafs and is 15-3-4 in its past 22 visits to Toronto.
Referee Chris Rooney left the game late in the second period, after being hit with the puck just seconds before Krejci's goal. He cradled his arm, but returned for the start of the third.
Before the game, fans stood and sang "O Canada" with their counterparts in Montreal and Ottawa as the anthem from the Canadian Tire Centre was shown on the scoreboard's big screen.
The pregame emotion didn't carry through as the Bruins went ahead early.
Soderberg opened the scoring on the power play at 3:27 after a fanned shot from Hamilton from the faceoff circle found Bergeron in front. Bernier stopped his redirect with his pad, but the puck went straight to Soderberg who had circled around the back of the net.
Bergeron moved past Adam Oates into sole possession of 13th place on the Bruins' career points list.
It took the Leafs 5:41 to get their first shot in the second period.
Krejci made it 2-0 at 15:58 of the second with a beautiful solo effort for his third of the season. Krejci drove at the Toronto goal, ignoring an attempted check by Phil Kessel, and swatted in his own rebound as he flew over Bernier.
The Leafs paid for a lapse on a power-play opportunity at 2:32 of the third as Campbell beat Phaneuf in front of the net to a pass from Daniel Paille and beat Bernier with five seconds remaining on the man-advantage.
Hamilton then beat the defense on a rush and scored on Bernier with a wrist shot at 4:09. That chased Bernier in favor of James Reimer.
The 6-foot-9 Chara injured the posterior cruciate ligament in his left knee during a hit on Islanders star John Tavares in front of the Boston net. Chara is expected to be out 4 to 6 weeks.
It was just the 21st game Chara has missed of a possible 622 games since joining the Bruins in July 2006.
It was Bernier's third straight start in goal. He was 1-2 in his four previous games against Boston with an .882 save percentage and 4.29 goals-against average.
The Maple Leafs have more Canadians (16) on their active roster than any other Canadian team. ... Toronto dressed seven defensemen and 11 forwards. ... Coming into the game, Toronto's top line of Kessel, Tyler Bozak and James van Riemsdyk had accounted for half of Toronto's 20 goals.